1. Field of the Invention
The present invention generally relates to tall support towers for large structures, such as wind turbine generators, microwave antennas or the like, and, more specifically, to tall support towers which are constructed of multiple telescopic sections that telescopically extend vertically to the tower""s full height and/or to tall support towers which are assembled at the site of installation in a generally horizontal position, and then tilted upwardly to a vertical position. The present invention incorporates both features into unique support tower structures.
2. Description of the Prior Art
Wind-powered windmills and turbines have been in use for many years for producing power for many purposes. Wind power to drive wind turbine generators to generate electrical energy have been used as an alternative energy source for many years, and the development of such uses of wind power is ongoing as exemplified by the following U.S. patents.
Initial development of wind turbine generators to produce electrical energy involved relatively small turbines and generators having a capacity of approximately 50 to 65 kilowatts, which were supported by small towers of approximately 50 to 75 feet in height. Towers of this height were typically fabricated from steel truss members of rectangular plan configuration and of lightweight construction. The lightweight construction enabled the towers to be initially positioned generally horizontally with the lower end pivotally connected to a foundation and the wind turbine and generator mounted at the upper end. The tower was then tilted upwardly to a vertical position by a cable and winch assembly or other power source to pull the tower to a vertical position on the foundation from the generally horizontal position. This tilting of the tower provided a relatively inexpensive installation that could be quickly and efficiently completed in a short time and required the use of only small and highly mobile erection equipment. A problem existed, however, in that as the tower was tilted into vertical position, the feet of the tower conflicted with anchor bolts that protruded from the foundation which would prevent the tower from setting flat on the foundation. This was resolved by bolting multiple steel adapter structures to the anchor bolts with the flat upper surface of each adapter receiving one of the feet of the tower. The tower feet were then bolted to the top of the adapters through matching bolt holes in the feet and top surface of the adapter.
More recent wind power generation included the development of larger and more efficient and cost-effective turbines capable of driving larger generators, having capacities up to approximately 750 kilowatts. The larger turbines and higher capacity generators required that taller support towers be provided in order to maximize the use of winds existing at higher elevations which have higher average speeds and smoother air flow characteristics than winds closer to the ground. In order to erect the larger towers to support the wind turbine generators at the higher elevations needed to maximize power production, heavy lift cranes with a lift capacity of up to 230 tons are used. The taller towers, either steel truss or tubular cross-sectional configuration are erected in sections by the crane and assembled in the vertical position. Each section of the tower is rigidly affixed to the adjacent tower sections by means of bolted connections. In the case of tubular cross-section towers the bolted connections are created through use of matching inwardly oriented flanges at each joint which contained matching boltholes to receive the bolts. The wind turbine generators are then mounted on top of the vertically oriented tower. This procedure is effective for towers up to approximately 180 feet in height with turbine and generator assemblies weighing up to approximately 60,000 pounds.
However, as the tower height increased along with the generating capacity and the weight of the wind turbine generator, the costs of installation increased materially. The transportation costs to move a heavy lift crane to a site of installation and then remove it from the site of installation, as well as the rental cost for a heavy lift crane, can be extremely high. A typical heavy lift crane with a lifting capacity of approximately 230 tons is barely capable of installing a 750 kilowatt wind turbine generator on a tower that is about 200 feet tall. Extra-heavy lift cranes with even higher costs are required for taller towers or heavier generators. Use of the extra-heavy lift cranes increases costs dramatically due to the very high rental and transportation costs of these larger units. Additional costs include the requirement for multiple large trucks and trailers for moving the extra-heavy lift crane to and from the job site, increased risk of serious accidents while traveling during movement of the crane to and from the job site, as well as at the job site, and increased wear and tear on public highways and plant site roads.
The massive size of extra-heavy lift cranes and their limited mobility require that work sites be well prepared to assure stability during the erection process. An extra-heavy lift crane work site requires extensive preparation of road bases with minimal tolerance for allowable slope of the road or for side to side pitch and crane working pads which require the use of heavy temporary matting beneath the cranes. Also, once on a job site, the cranes need to be moved frequently from one wind turbine foundation to another which further adds to high maintenance costs on the cranes and roads and expensive time-consuming moving procedures. This is especially problematic at preferred and available job sites which are usually near the top of hills, ridges or mountains which require erection equipment to be highly mobile in order to minimize erection time and cost. Use of the extra-heavy lift cranes means that many of the best sites cannot be used due to the excessive cost of road and pad construction needed for the larger cranes.
Heavy lift cranes are typically near their maximum safe working ranges when erecting wind turbine generators of 600-750 kilowatt capacity on towers as high as 200 feet. This condition makes it necessary to suspend erection work during winds in excess of 20 to 25 miles-per-hour in order to avoid excessive wind loads on the long crane booms and on the structure being lifted that exceed the safe working loads of the crane. In job sites where such towers are erected, it is not unusual for erection work to be delayed for several days during a windy season and work is frequently delayed due to inclement weather such as rain, ice accumulation or snow. Other constraints associated with heavy and extra-heavy lift crane use include requirements for good visibility so that the operator can see hand signals given by a loadmaster, limited availability of extra-heavy lift cranes during periods of high construction activity, limited availability of extra-heavy lift cranes capable of erecting wind turbine generators having a capacity greater than 750 kilowatts and the time and large number of equipment components necessary to move larger capacity lift cranes to and from the site of tower erection.
The cost and availability of extra-heavy lift cranes has become a serious limiting factor to further economic development of wind energy especially in view of the ongoing development of wind turbine generators having a capacity of up to approximately 2,500 kilowatts. Such generators will require towers as tall as 350 feet in height with turbine generator combinations weighing in excess of 150,000 pounds. Accordingly, the use of increasingly heavier wind turbine generators mounted on ever taller towers has reached a point where the cost of construction has become a significant constraint to further development. Likewise, the limited availability of extra-heavy lift cranes capable of erecting such taller towers and installing heavier wind turbine generators at the upper end thereof have introduced additional serious constraints on the development of wind-powered electrical energy generation.
While the above-identified patents and prior developments in the construction of supporting towers for wind-powered energy include towers which are pivotally supported for tilt-up erection, sectional tower constructions and telescopic tower constructions, the prior art does not disclose a tower assembly incorporating these features which can be constructed to a height and weight capacity necessary to support the larger wind turbine generators without the use of extra-heavy lift cranes.
In order to overcome the constraints described above in connection with tall towers for large and heavy wind turbine generators, the present invention provides a tall tower capable of supporting a heavy wind turbine generator that starts out as multiple independent tubular tower sections which are nested inside each other while in a generally horizontal position. The number of tower sections is dependent on the desired tower height and configuration and may require two, three or four, or even more, tower sections. The nested sections are appropriately interconnected so as to be internally spaced one from another while oriented in a generally horizontal position at the job site prior to erection. The outermost tower section has a lower edge pivotally connected to the tower supporting foundation by means of a removable hinge structure.
A unique cable, pulley, winch and gin pole structure is then used to tilt the generally horizontal nested sections to an upright vertical position. The wind turbine generator may be mounted on the top end of the innermost tower section either before or after the nested tower sections are tilted to their upright vertical position. Once tilted into their vertical position, the nested tower sections are secured onto the foundation by a flange at the lower end of the outer tower section which is secured to the foundation by a plurality of bolt arrangements. The hinge mechanism is then removed for use on subsequent tower installations. The inner tower section or sections and the wind turbine generator are then telescopically raised to the final elevated position by a unique elevating and guiding mechanism that extends the inner tower section or sections to the maximum vertical height of the tower. Once extended to full height, the tower sections are fastened together to form a rigid structure by means of matching but oppositely oriented flanges with matching boltholes. By combining a tilting and telescoping tower assembly, the necessity for using extra-heavy lift cranes at the job site can be eliminated. Additionally, the towers can be telescopically lowered for maintenance access purposes, eliminating the need for extra-heavy lift cranes during maintenance.
The unique portable gin pole mechanism of the present invention is preferably a lattice frame structure having its lower end pivotally connected to the tower foundation in spaced opposed relation to the pivotal connection between the outer tower section and the foundation. The gin pole is attached to the foundation by pivotal connections while in a generally horizontal position and then raised from a generally horizontal position and oriented in a position angled outwardly in relation to the final vertical position of the nested tower sections when they are vertically positioned. An inexpensive light-weight crane assists in initially raising the outer end of the gin pole, from its beginning horizontal position and then the weight of the at rest tower and wind turbine generator is used as a counterweight in raising the gin pole to its upright position by operating the winch and tightening the cable that is associated with the winch. The upper end of the gin pole and the upper end of the outer tower section tilt the gin pole structure upwardly about the pivotal connections between the base of the gin pole and the foundation.
The gin pole is then anchored in its upwardly angled position. The nested tower sections are then tilted upwardly to their vertical position by a winch mounted on the foundation with a cable and pulley arrangement associated with the upper end of the gin pole and the upper end of the outer tower section. The nested tower sections are thus tilted upwardly about the pivotal connection between the outer tower section and the foundation.
Recessed anchor bolts consisting of high strength threaded rods topped with threaded couplers are embedded in the concrete foundation flush with the top of the foundation. The couplers receive high strength bolts that rigidly affix the base or anchor plate of the vertically oriented outer tower section to the foundation. Use of the threaded couplers flush with the foundation top surface allows the nested tower sections to be tilted into place without conflicting with embedded anchor bolts that otherwise extend above the surface of the concrete foundation.
After the nested tower sections are positioned in their vertical position and the outer tower section is rigidly bolted to the foundation, the lifting mechanisms in the tower are activated to extend the nested tower sections. In a preferred embodiment, the lifting mechanism between the outermost tower section and the adjacent or second tower section nested inside the outermost section is a jacking mechanism, and the lifting mechanism between the second tower section and additional tower sections, such as a third and perhaps fourth tower section, is a cable and pulley mechanism. The cable and pulley mechanism interconnects each of the innermost upper tower sections preferably in a manner such that all of the innermost upper nested tower sections automatically extend when the jacking mechanism extends the second tower section from its nested relationship within the outer lowermost tower section.
Alternatively, additional jacking mechanisms in lieu of the cable and pulley mechanism may be positioned internally of the second tower section to engage and lift the lower end of the third tower section, and similarly for additional tower sections, if used. The multiple jacking mechanisms can be operated simultaneously or independently through the use of manual controls or a computerized control system, giving full control of the telescoping operation.
The lifting mechanisms further include a guide system to guide the tower sections as they telescope vertically with respect to each other. A preferred guide system includes inner and outer rollers interacting between adjacent tower sections. The guide system associated with the cable and pulley mechanism acts in a manner to bias the rollers into engagement with internal and external surfaces of the tower sections as they are being extended. This biasing engagement of the rollers prevents relative lateral movement between tower sections so that adjacent tower sections do not come into contact with each other, which would cause damage to hardware installed on the inner surfaces of each tower section.
The jacking mechanism is positioned internally of the outermost lower tower section and includes crawler jacks positioned on vertical, parallel jackrods extending between the upper and lower ends of the outermost lower tower section. The crawler jacks are positioned below the second tower section and engage the lower end of the second tower section to lift it upward, or lower it downward. The inner guide rollers associated with the jacking mechanism are affixed to the lower structure of the second tower section and engage the internal surfaces of the lowermost tower section as the second section is being extended. The outer guide rollers are affixed to the upper flange of the lowermost tower section and engage the external surface of the second tower section. These guide rollers also prevent lateral movement of the second tower section so that the first and second tower sections do not come into contact with each other, which would cause damage to hardware installed on the inner surface of the first tower section.
Also in accordance with the present invention, the floor of the foundation is preferably recessed below the base of the support tower for mounting electronic controls and switchgear required for operation of the wind turbine generator. Recessing the floor in this manner allows the controls and switchgear to be mounted on the foundation prior to assembly and erection of the tower sections and provides sufficient clearance between the bottom tower section and the switchgear when the tower is tilted into the vertical position such that the switchgear does not conflict with erecting the tower.
It is therefore an object of the present invention to provide a tilt-up telescopically sectional tower for supporting a large load at the tower top such as a wind turbine generator, microwave communication equipment, high voltage electrical transmission lines and the like.
Another object of the present invention is to provide a support tower for a wind turbine generator in which the tower includes a plurality of telescopically associated tower sections that are horizontally supported with an outer lowermost tower section hingedly connected to a supporting foundation. The nested tower sections are tilted upwardly to a vertical position and securely anchored to the foundation. The tower sections are then telescopically extended vertically to elevate the wind turbine generator to a fully extended position.
Still another object of the present invention is to provide a support tower including a plurality of nested telescoped tower sections of decreasing cross-sectional area from a lower tower section to an upper tower section. The tower sections are horizontally positioned and then tilted to a vertical position and securely anchored to the foundation. The tower load, such as a wind turbine generator or the like, is mounted on the upper end of the uppermost tower section either before or after the nested tower sections are tilted into the vertical position, after which the tower sections are extended to their full vertical height to position the tower load in an elevated position.
A further object of the present invention is to provide a support tower in accordance with the preceding objects in which the erection process can be safely and quickly performed by a small crew of personnel while maintaining complete stability of the tower sections during erection with the elevating process being reversible in the event it is necessary to lower the load supported at the upper end of the tower for maintenance or replacement purposes.
Still another object of the present invention is to provide a support tower for supporting heavy structures at a high elevation in accordance with the preceding objects in which the cost of erection is minimized by utilizing equipment that can be easily transported to and from the site of erection, requiring the use of a minimum number of personnel during the erection procedure, enabling the erection process to be completed in a safe and efficient manner in adverse weather and lighting conditions and enabling heavy structures to be supported from the tower by tilting the tower from a horizontal position to a vertical position and then extending telescopic tower sections to a full vertical height of the tower.
Yet another object of this invention to be specifically enumerated herein is to provide a tilt-up and telescopic tower for wind turbines and other structures in accordance with the preceding objects and which will conform to conventional forms of manufacture, be of simple construction and easy to use so as to provide a support tower that will be economically feasible, long lasting and relatively trouble free in operation.
These together with other objects and advantages that will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.